NH4+, or ammonium, is a positively charged ion formed when ammonia (NH3) accepts a proton (H+). It plays a crucial role in various biological and chemical processes, including nitrogen cycling in ecosystems. Ammonium is commonly found in fertilizers, helping plants absorb nitrogen, which is essential for their growth. In aqueous solutions, NH4+ can exist alongside its counterpart, NH3. The balance between these two forms is influenced by factors such as pH and temperature. Ammonium is also important in wastewater treatment, where it is converted into less harmful substances through microbial processes.